INTRODUCTION

There is a high prevalence of depression in older adults, either clinically diagnosed or with a recognized depressive symptom-atology, reportedly between 7 and 49% (1). Despite this inci-dence, it has been estimated that 70-90% of depression in old age is undiagnosed, misdiagnosed, or dismissed as a normal part of aging.
The objective is to increase the state of wellbeing and quality of life of the population, and especially the elderly. Quality of life is influenced by numerous factors, including certain food habits such as the consumption of fruits, vegetables, olive oil, fish and wine (in moderation), all distinguishing features of the Mediterra-
nean diet, which has been associated with the ability to prevent cognitive deterioration, lower cardiovascular risk and decreased mortality from all causes (2). There is growing evidence that diet –a modifiable lifestyle factor– could be one component of an effective prevention strategy against depression, although no firm conclusion can be drawn at this point (3). A healthy Mediterra-nean dietary pattern appears to be associated with lower odds of depression and favourable mental and physical health outcomes (4). The Mediterranean dietary pattern refers not only to the type of food consumed, but also to lifestyle and the social customs associated with the way of eating. It therefore seems reasonable to assume that this pattern of healthy eating can modify cognitive status (4,5) and reduce the prevalence of depression in the elderly population (6).There is a wealth of observations and experimental knowl-edge showing that effective brain function depends on an adequate and constant supply of nutrients, and that nutrition –particularly of micronutrients and w-3 polyunsaturated fatty acids– is key for cognitive performance and mental wellbeing (7). The Mediterranean dietary pattern is rich in plant foods and fish. Plant foods have a high content in minerals, vita-mins and natural antioxidants, and fish is a good source of w-3 polyunsaturated fatty acids (2). The elderly population is at higher risk of receiving insufficient levels of these micro-nutrients that are essential for proper brain functioning, and whose deficiency negatively influences cognitive performance and is associated with age-related cognitive decline (5) and depressive symptoms (6). Interest in old-age depression has increased due to the ageing population and the increasing demographic importance of elderly people. The study of these variables is interesting at any age, but it has a greater impact on the prevalence of morbidity and mortality when studied in older people. However, there are very few studies in the over-75 y.